The manufacture of N-alkyl polyhydroxy amines, such as N-methylglucamine, has been known for many years, and such materials are available commercially. In the main, however, their use has been somewhat limited and such materials have been relatively expensive. Recently, there has been occasion to employ N-alkyl polyhydroxy amines in reactions with fatty acid esters to prepare fatty acid polyhydroxy amide detersive surfactants for use in cleaning products. As can be imagined, were the cost of N-alkyl polyhydroxy amines to remain high, this laundry detergent use of the fatty acid polyhydroxy amide surfactants would be impossible. Accordingly, there is a continuing search for quick, inexpensive means for preparing N-alkyl polyhydroxy amines on a commercial scale.
Moreover, it is has been determined that care must be taken in preparing N-alkyl polyhydroxy amines in a form that is suitable for subsequent reaction with fatty acid methyl esters, since contamination of the N-alkyl polyhydroxy amines with, for example., hydrogenation catalysts such as Raney nickel, unreacted sugars, water, and the like, can seriously impact on the formation of the fatty acid polyhydroxy amide formation. For example, browning reactions, with the formation of undesirable color bodies, can occur. The formation of various undesirable by-products such as cyclic materials and/or ester-amides can also occur. In a worse case scenario, by-product formation can be so high that the desired reaction of the N-alkyl polyhydroxy amine with the fatty acid methyl ester is essentially stopped in its entirety, with the formation of black, intractable tarry products.
The present invention provides a simple means for preparing N-alkyl polyhydroxy amines, especially N-methylglucamine, in high yields, with low color formation, and in a form that is particularly suited for subsequent reaction with fatty acid esters.